40KHz? Are you receiving me?

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- 28th September 2009, 01:45
CumQuaT

40KHz? Are you receiving me?

Hi everyone,

Has anyone used a PIC (coded with PicBasic Pro) to accurately receive a 40KHz infrared signal before? I'm not sure wether it is do-able or not, so I figured I'd ask you fine people to see if anyone's done it before and if so, what would the code be?

Just to give more info on what I'm doing, the signal I'm trying to receive is as follows:

3ms on
6ms off
3ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on

So yeah, any help would be awesome. Thanks.
- 28th September 2009, 02:39
DaveC3

Here is a IR remote code I used way back for a Remote Robot using a Sony remote control.

Hope it helps

Code:

define LOADER_USED 1 DEFINE OSC 20 start: ADCON1 = 7 'angleVar VAR BYTE ' set up constants with the minimum and maximum pulsewidths 'SERVO1 CON 450 'SERVO2 CON 1000 ' set up a constant with the time between pulses: refreshPeriod CON 20 A VAR BYTE ' set an initial pulsewidth: 'angleVar = minAngle TRISB = 0 TRISA = %00000100 P_VAL VAR WORD IR_DEV VAR BYTE IR_BUT VAR BYTE HEADER VAR WORD BITCNT VAR BYTE PACKET VAR WORD DIRINF VAR BYTE SEROUT2 PORTC.6,32,["START " , 10,13] main: GOSUB IRIN SELECT CASE IR_BUT CASE $10 GOSUB LEFT CASE $11 GOSUB RIGHT CASE $12 GOSUB FWD CASE $13 GOSUB RE CASE $14 GOSUB ST CASE ELSE END SELECT GoTo main 'Recieve a signel from a Sony remote control ' and return with a 7 bit button code ' IR_BUT and a 5 bit device code IR_DEV in the variable IR_DEV ' if no header then IR_DEV and IR_BUT hold 255 IRIN: IR_DEV = 255:IR_BUT = 255 PULSIN PORTA.2,0,HEADER 'Measure header IF HEADER < 1000 THEN RETURN IF HEADER > 1350 THEN RETURN ' VERIFY GOOD HEADER IF BAD RETURN FOR BITCNT = 0 TO 11 PULSIN PORTA.2,0,P_VAL IF p_VAL >= 450 THEN PACKET.0[BITCNT] = 1 ELSE PACKET.0[BITCNT] = 0 ENDIF NEXT 'Split the 7 bit button code and the 5 bit device code IR_BUT = PACKET & %01111111 IR_DEV = (PACKET>>7) & %00011111 SEROUT2 PORTC.6,32,["BUTTON =", HEX IR_BUT, 10,13] RETURN FWD: FOR A = 1 TO 20 Low PORTB.7 Low PORTB.6 ' pulse the pin PulsOut PORTB.7, 450 PulsOut PORTB.6, 1000 ' pause for as long as needed: Pause refreshPeriod NEXT A RETURN RE: FOR A = 1 TO 20 Low PORTB.7 Low PORTB.6 ' pulse the pin PulsOut PORTB.7, 1000 PulsOut PORTB.6, 450 ' pause for as long as needed: Pause refreshPeriod NEXT A RETURN ST: Low PORTB.7 Low PORTB.6 'PAUSE 1000 RETURN LEFT: FOR A = 1 TO 20 Low PORTB.7 Low PORTB.6 ' pulse the pin PulsOut PORTB.7, 1000 PulsOut PORTB.6, 1000 ' pause for as long as needed: Pause refreshPeriod NEXT A RETURN RIGHT: FOR A = 1 TO 20 Low PORTB.7 Low PORTB.6 ' pulse the pin PulsOut PORTB.7, 450 PulsOut PORTB.6, 450 ' pause for as long as needed: Pause refreshPeriod NEXT A RETURN
- 28th September 2009, 02:44
Kamikaze47

You should be able to use the PULSIN command to measure the length of the pulses, but we will need more info to give further help.

I assume you have an IR receiver hooked up to one of your I/O pins?

Is the IR signal coming from a remote control? If so, what is the remote for, and what brand is it? Do you know the encoding scheme its using?
- 28th September 2009, 10:07
comwarrior

ET phone home?
- 28th September 2009, 10:29
ardhuru

From the figures you have given, it looks like the modulation frequency might be 40 kHz; the actual data is slower. So, as long as your IR receiver module can handle 40 kHz, decoding the data (pulse widths and spaces), which is in milli seconds, should most certainly be within the scope of PBP.

Depending on the range you expect, even a generic 36 - 38 kHz IR module should work fine at 40 kHz.

Anand
- 29th September 2009, 00:51
CumQuaT

reply

Hi all,

Thanks for the responses. Sorry it takes me so long to respond. I'm in Australia, so with the time differences all of your responses come in while I'm asleep.

I'm using a 40KHz phototransistor to receive, yes, and interfacing it to a PIC16F628A oscillating at 4MHz.

Thanks for the example code, DaveC3. It's not a remote control that I'm trying to read from, but I imagine it's a similar process across the board. I'll pick that code apart and see what I can come up with.